The oil industry produces large amounts of waste water during exploration and production of petroleum. It has been estimated that approximately 800 gallons of water are used for the production of a barrel of oil of which approximately 80% is used for cooling in the refinery process. Oil wastes are classified depending on their origin, e.g., from oil production or from oil refining. Waste water from oil production is generally a mixture of drilling muds, salt water, free and emulsified oil and natural gas. Waste water from oil refineries includes, inter alia, free and emulsified oils from leaks, spills, and other sources. The combined refinery wastes or spills may contain crude oil and various fractions thereof, dissolved or suspended mineral and organic compounds discharged in liquors and sludges in various stages of processing.
Cleaning of industrial waste water from oil production and oil refining is important for both environmental and industry purposes. There are many conventional processes for cleaning oil industrial waste water which include, for example, gravity separation, floatation, filtration, chemical treatments, electrochemical treatments, biochemical treatments, and the like. These systems are typically large, inefficient, and expensive to operate. The only known process which can achieve a final effluent with less than 5 p.p.m. oil contaminants is membrane filtration. However, membrane filtration is expensive and difficult to operate because the membranes quickly foul.